1. Field of the Invention
The present invention relates to a passive vibration isolating system.
2. Description of the Related Art
The closest prior art of which the applicant is aware is disclosed in U.S. Pat. No. 4,320,549 to Greb, filed on Jul. 5, 1979, entitled "ROCKER-SLIDING BEARING ASSEMBLY AND A METHOD OF LINING THE ASSEMBLY".
A first conventional passive vibration isolating system in accordance with the prior art shown in FIGS. 7-9 comprises a plurality of lead rubber bearings 80 each of which is mounted between a building 62 and a ground base 60. Each of the lead rubber bearings 80 includes a base plate 81 fixedly mounted on the ground base 60, a supporting plate 82 fixedly mounted on an underside of the building 62, a rubber pad 83 supported between the base plate 81 and the supporting plate 82, and a lead column 84 mounted in a center of the rubber pad 83 and located between the base plate 81 and the supporting plate 82.
In operation, when an earthquake occurs, the base plate 81 is moved with the ground base 60 along the direction indicated by an arrow as shown in FIG. 9 to exert a shearing force on the lead rubber bearing 80, thereby deforming the rubber pad 83 and the lead column 84. In the meantime, the supporting plate 82 together with the building 62 is only slightly displaced by means of a plastic deformation or yielding effect of the lead column 84, thereby decreasing the displacement of the building 62 due to the sliding motion of the ground base 60, and thereby efficiently isolating the building 62 from the vibration created by the earthquake.
Referring to FIG. 8, the displacement A of the building 62 fitted with the lead rubber bearing 80 is much smaller than the displacement B of the building 62 without the lead rubber bearing 80. However, the rubber pad 83 will be worn out after long-term utilization, thereby decreasing the vibration isolating effect. In addition, the building 62 cannot be returned to its original position due to the plastic deformation of the lead column 84, thereby causing a deviation in the position of the building 62.
A second conventional passive vibration isolating system in accordance with the prior art shown in FIG. 10 comprises a plurality of pot bearings 90 each of which is mounted between a building (not shown) and a ground base (not shown). Each of the pot bearings 90 includes a base plate 91 fixedly mounted on the ground base and defining a recess 912 therein, a synthetic rubber 94 received in the recess 912, a bearing disk 93 fixedly mounted on the synthetic rubber 94, an elongated guiding rail 95 fixedly mounted on the bearing disk 93, a supporting plate 92 fixedly mounted on the underside of the building and defining a guiding groove 922 to slidably receive the guiding rail 95 therein, and a wear-resistant resin 96 coated between the bearing disk 93 and the supporting plate 92.
In operation, the supporting plate 92 together with the building can slide on the wear-resistant resin 96 along the guiding rail 95 when an earthquake occurs, thereby greatly decreasing the vibration caused by the earthquake. However, it is necessary to provide a damping mechanism for returning the building to its original position. In addition, the supporting plate 92 can only move along one direction, thereby greatly limiting the versatility of the pot bearing 90.
The present invention has arisen to mitigate and/or obviate the disadvantage of the conventional passive vibration isolating systems.